LONDON, ENGLAND - JANUARY 09: A general view during the Netflix UK launch in London, England on January 9, 2012. Netflix the leading global internet subscription service for films and TV programmes, launches today in the United Kingdom and Ireland, offering instant and unlimited access to a broad range of entertainment for the low monthly price of £5.99 in the UK and €6.99 in Ireland. (Photo by Gareth Cattermole/Getty Images for Netflix)

A federal judge has taken a step toward requiring Netflix to provide closed-captioning for the deaf on its video-streaming website, ruling that federal disability laws cover businesses that serve their customers online.

Netflix, headquartered in Los Gatos, is the dominant provider of movies and TV programs on the Internet, with more than 20 million subscribers. The National Association for the Deaf accused the company of violating the law by withholding closed-captioning from most of the videos on its "Watch Instantly" on-demand website.

Netflix sought to dismiss the suit, arguing that the Americans with Disabilities Act requires accommodations for the disabled only in stores and other physical structures - an argument accepted in the past by some courts, including the Ninth U.S. Circuit Court of Appeals in San Francisco.

On Tuesday, however, U.S. District Judge Michael Ponsor of Springfield, Mass., said the law prohibits discrimination in any venue, including the Internet.

The legislative history of the 1990 law "makes clear that Congress intended the ADA to adapt to changes in technology," Ponsor said. "In a society in which business is increasingly conducted online," he said, the law's goal of equal access would be frustrated by "excluding businesses that sell services through the Internet."

The ruling allows the suit to proceed on behalf of groups representing the deaf and hard-of-hearing, who still must prove that the ADA requires Netflix to provide closed-captioning. Their advocates nonetheless called it a significant victory.

"By recognizing that websites are covered by the ADA, the court has ensured that the ADA stays relevant as much of our society moves from Main Street to the Internet," said Arlene Mayerson of the Disability Rights Education and Defense Fund in Berkeley, a lawyer for the plaintiffs.

Netflix could appeal the ruling to a federal appeals court in Boston. Spokesman Joris Evers said the company had no comment.

A 1996 federal law required closed-captioning for television programs but did not address online videos. Federal Communication Commission regulations will require captioning on Internet videos of all U.S.-produced, post-1996 programs by March 2014.

Netflix argued that the FCC rules took precedence over the more generally worded Americans with Disabilities Act. But Ponsor said that the FCC's timeline "reflects only minimum compliance standards" and that a court could invoke the ADA to order closed captioning at an earlier date on all videos.